1. Field of the Invention
The present invention relates to a novel ruthenium-phosphine complex represented by the following general formula (1) and to an asymmetric hydrogenation catalyst comprising the complex. EQU [{RuX(L)}.sub.2 (.mu.-X).sub.3 ].sup.- [R.sup.2.sub.2 NH.sub.2 ].sup.+ (1)
2. Description of Prior Art
Many organic synthetic reactions using a transition metal complex as the catalyst have been developed and exploited to achieve various objects. In particular, there have been many reports concerning asymmetric catalysts used in an asymmetric hydrogenation reaction. There have been many studies in which complexes comprising a transition metal atom and an optically active phosphine are used as an asymmetric hydrogenation catalyst since a report was made that a complex containing, as the ligands, a rhodium atom and an optically active phosphine was selectively used as an asymmetric hydrogenation catalyst to prepare an optically active compound with high enantiomer excess.
For example, in J. Chem. Soc., Chem. Commun. (1985), 922 and J. Chem. Soc., Perkin Trans. I, (1987), 1571, technologies are disclosed in which an acylaminoacrylic acid derivative is hydrogenated using 2,2'-bis(diphenylphosphine)-1,1'-binaphthyl-ruthenium complex (Ru.sub.2 Cl.sub.4 (BINAP).sub.2.multidot.Et.sub.3 N, which is hereinafter called "BINAP-Ru complex") to produce an optically active amino acid derivative.
Recently, a ruthenium complex of p-MeO-BINAP, namely, [{RuCl(p-MeO-BINAP)}.sub.2 (.mu.-Cl).sub.3 ].sup.- [Et.sub.2 NH.sub.2 ] .sup.+ has been disclosed in Organometallics, 15 (1996), 1521. Moreover, Japanese Patent Application No. 8-359818 discloses an asymmetric hydrogenation reaction of ketones by using ((5,6), (5', 6')-bis (methylenedioxy)biphenyl-2,2'-diyl)bis(diphenylphosphine)-ruthenium complex (hereinafter called "SEGPHOS-Ru complex").
However, the ruthenium complexes used in Japanese Patent Application No. 8-359818, for example, are complicated in the preparation of the complexes, have a problem in stability and yield and production of complicated mixtures. These complexes also have insufficient catalytic activity and durability.
Ruthenium metals are relatively inexpensive among transition metals and are expected to serve as an industrially advantageous catalyst. These catalysts, however, have unsolved problems in the preciseness and application of reaction. Hence there is a demand for catalysts which can be easily produced, are inexpensive, have a high activity and durability, and can give a enantiomer excess in an asymmetric reaction, making products of optically high purity.